# 类定义
class Node:
    # 构造函数？ 传输参数 弱类型参数 x
    def __init__(self, x):
        # 定义三个属性
        self.val = x
        self.left = None
        self.right = None


if __name__ == "__main__":
    print("appication starting")
    # 对象创建并赋值给a
    a = Node(2)
    a.left = Node(3)
    print(a.val)
    print(a.left.val)
    pass
